Effect of injection parameter and PODE addition on ultrafine particles of a F-T diesel engine and its distribution analysis

Coal-based Fischer-Tropsch (F-T) diesel and polyoxymethylene dimethyl ethers (PODE) show significant potential in reducing particulate matter (PM) emitted from direct injection compression ignition engines. In this study, the influence of fuel properties and injection parameters on PM reduction was investigated on a common-rail six-cylinder heavy engine. The petroleum diesel (marked as D100), F-T diesel (marked as FT100) and a blend of 80 % F-T diesel and 20 % PODE (marked as FTP20) were chosen as test fuels. The results show that, compared with D100, FT100 and FTP20 have earlier ignition timing, lower premixed and milder combustion, while FTP20 has longer combustion duration due to its low heating value and high injection pulse width. With the addition of PODE, the ultrafine particles with a diameter >100 nm significantly decrease, while the ultrafine particles with a diameter less than 50 nm increases, and the size of ultrafine particles from 50 to 100 nm almost decreases. As the injection timing (θ_in) advances and common-rail pressure (P_cr) increases, the distribution of particle shifts towards smaller sizes, and the bimodal distribution are observed. Furthermore, the distribution fitting of particle size is conducted using Gaussian and Gamma distribution. It is concluded that Gamma distribution can better replicate the bimodal distribution trend of UFPs under various fuels types, θ_in and P_cr, facilitating the further analysis of ultrafine particles. In summary, coupling injection parameter and PODE addition is an effective way to improve particulate emissions for F-T diesel, and Gamma distribution can be applied to predict the size distribution of UFPs and help generate control strategies under various parameters.